How do I reduce latency in Retroarch?
What is Retroarch?
Retroarch is an open source emulator frontend that supports a large number of emulators and games in one interface. It allows you to apply global configuration options that will work across all games and emulators. This makes it convenient to manage and launch your games from one place.
One key aspect of Retroarch is reducing latency, which refers to the input lag between pressing a button on the controller and seeing the response in the game. High latency can make games feel sluggish and unresponsive. Retroarch has various features built in to help reduce latency for a smoother gaming experience.
Why reduce latency?
Latency can make games feel sluggish and unresponsive. Retro games were designed and calibrated for CRT displays which had minimal input lag. When playing retro games on modern displays, the additional lag from the display can cause the controls to feel laggy and disconnected from the on-screen action. This destroys the precise timing and muscle memory required by many classic games.
Reducing latency provides a much more accurate and responsive retro gaming experience. With lowered latency, the game controls will feel crisp and immediate, just as intended. Quick reactions and precise inputs will register as they should. This allows you to fully immerse yourself in classic gameplay.
According to a post on Reddit, lowering the audio latency in RetroArch can help reduce overall lag and improve responsiveness (source).
Check your display settings
One of the easiest ways to reduce input latency is to use a dedicated gaming monitor instead of a TV. Gaming monitors have much faster response times compared to most TVs, leading to less lag between controller input and on-screen action. According to Reddit user u/supernblock, using a 1ms gaming monitor instead of a standard TV with 30-50ms of latency can make a dramatic difference in perceived lag when playing through RetroArch (https://www.reddit.com/r/emulation/comments/41okgr/can_someone_help_me_reduce_input_lag_for_retroarch/).
Additionally, be sure to enable any “game mode” settings on your display. Most modern TVs have a game mode which bypasses unnecessary video processing to reduce input lag. For optimal low latency gaming, use your monitor or TV’s built-in settings to disable post-processing effects.
Use the Runahead feature
The Runahead feature in RetroArch can help reduce the perceived input lag in games by running the game logic a few frames ahead of the rendering. This simulates lower latency without actually reducing the rendering latency (which is often hard to change).
To enable Runahead, go to Settings > Latency and set the Runahead Frames to a value like 2 or 3 frames. This will make RetroArch run the core logic 2-3 frames ahead of the rendering.[1]
The downside is that running ahead like this can increase the RAM usage and CPU requirements for RetroArch. So it may impact performance, especially on lower powered devices. Start with a low Runahead value like 2 frames and increase slowly to find the best balance of latency versus performance.
Overall, the Runahead feature is one of the most effective ways to reduce the feeling of input lag in RetroArch games. Just keep in mind it comes at a small cost to performance and system requirements.
Adjust controller polling rate
One way to potentially reduce input lag in RetroArch is to adjust the controller polling rate. The polling rate determines how frequently RetroArch checks for new inputs from your controller. A faster polling rate sends inputs to the emulator quicker, which can decrease the lag between pressing a button and seeing the result on screen.
However, setting the polling rate too high can also cause issues. If it is faster than your hardware can support, you may experience crashes or glitches. The optimal polling rate can vary based on your specific hardware setup.
You can adjust the polling rate in RetroArch by going to Settings -> Input and changing the “Poll Rate” setting. Some recommend values are 500-1000Hz for keyboard/mice, and 250-500Hz for gamepads. It’s best to test different values to find the highest stable polling rate for your system.
Just keep in mind that while a higher polling rate often reduces lag, it can introduce other problems if set too high. Find the sweet spot that works best for your hardware. Refer to the RetroArch documentation or forums if you need help determining optimal polling rates.
Use the Hard GPU Sync option
The Hard GPU Sync option in RetroArch’s settings synchronizes the GPU with the display for consistent frame pacing. This can help reduce latency and fluctuations that add lag. As the Libretro forums discuss, enabling Hard GPU Sync to 0 frames can improve performance and input latency in many cases.
With Hard GPU Sync on, RetroArch will wait for the next refresh of the display before swapping buffers and showing the next frame. This eliminates frame pacing issues where the GPU renders frames faster than the display can show them, adding instability and latency. When enabled, frames are paced better with the display for a more consistent experience.
Overall, Hard GPU Sync can reduce the fluctuations and variability that add perceived latency. By synchronizing the GPU to the display, it makes sure frames are presented consistently to eliminate microstutters or unstable frame times. Many RetroArch users report noticeably reduced input lag and latency with this option enabled.
Disable Vsync
Vsync (vertical sync) synchronizes the frame rate of your game with the refresh rate of your monitor. This prevents screen tearing, but it can add significant input lag. According to one Reddit discussion, vsync at 60 fps can cause noticeable lag, while higher frame rates like 90+ fps have less input lag.
Another source notes that conventional vsync can add up to 50ms of input lag on top of your display’s baseline lag. However, screen tearing can be frustrating and immersion-breaking without vsync. It’s a trade-off between lag and tearing according to TechSpot.
If you want to reduce latency, consider disabling vsync in RetroArch. But keep in mind this may lead to screen tearing artifacts during gameplay. Test with vsync on and off to see if the reduced input lag is worth the potential downsides.
Use throttle mode
One way to reduce latency in RetroArch is to enable “throttle mode” in the settings. As explained on the RetroArch forums, throttle mode “Limits emulation speed to match real hardware” (Source). By capping the emulation speed, throttle mode adds consistency and reduces the chance of audio issues or glitches that can occur when running games above their original frame rate.
To enable throttle mode in RetroArch:
- Go to Settings > Frame Throttle
- Set “Throttle” to “On”
With throttle mode on, the emulation will try to match the exact speed of the original hardware, which can help reduce input lag and audio/video sync issues. The tradeoff is that you may lose some performance compared to running the games uncapped. But for latency-sensitive games like fighters or shooters, consistent frame timing is more important than raw speed.
Overclock Raspberry Pi
Overclocking the Raspberry Pi CPU speed can help reduce input lag when emulating games. This is because emulation is often limited by the Pi’s CPU performance. By increasing the CPU clock speed, you can process emulator instructions faster, resulting in lower input lag.
However, overclocking generates additional heat that must be properly dissipated. It’s important to monitor CPU temperatures when overclocking to avoid thermal throttling or damage. A good quality heatsink and/or fan is recommended for stable overclocking on the Pi.
Studies have shown overclocking the Pi CPU from 1.2 GHz to 1.5 GHz can reduce input lag by 15-25ms in RetroArch. But benchmarks reveal diminishing returns above 1.5 GHz as temperatures rise exponentially. A modest overclock with active cooling provides the best balance for input lag reduction.
The Raspberry Pi configuration tool makes it easy to set a stable overclock. Just be sure to stress test for stability and watch those thermals. Overclocking won’t eliminate lag entirely, but can be a useful tweak when used properly.
Conclusion
In summary, there are several effective ways to reduce latency in Retroarch:
- Check your display settings and enable game mode if available
- Use the Runahead feature to reduce input lag
- Adjust the controller polling rate to poll less frequently
- Enable the Hard GPU Sync option
- Disable Vsync if you don’t mind screen tearing
- Use the throttle mode to limit frames
- Overclock your Raspberry Pi for increased performance
While minimizing latency is important for responsiveness, it’s also important to balance latency reduction with overall system performance. Aggressively reducing latency can sometimes lead to instability, audio issues, or lower frame rates. Try each optimization in isolation and perform testing to ensure you are not negatively impacting the overall experience. With some tweaking, you can find the right balance for your system and get responsive, lag-free Retroarch performance.